Attention has been paid to an extracorporeal therapy using ultrasonic waves or heavy particle beams such as HIFU (High-Intensity Focused Ultrasound) or an extracorporeal shock wave lithotripsy as a useful therapy that is low in the physical load of a patient and is capable of expecting a reduction in the therapeutic period since the invasiveness is low, and QOL (Quality of Life) after therapy is high. However, in order to conduct a low-invasive therapy, it is essential to visually perceive the motion of an object and a change with age. In particular, the motion due to the movement of a person to be examined and the motion due to a respiratory movement or peristalsis are accurately estimated, and the three-dimensional movement of the object is grasped, thereby making it possible to expect the more accurate low-invasive therapy.
Hereinafter, a description will be given of a conventional motion detecting method and a therapeutic device using the motion detecting method.
Patent Document 1 (Japanese Patent Laid-Open No. 2000-237205) has reported a method of detecting a motion and conducting an ultrasonic therapy by using an ultrasonic transducer that is attached to a mechanism which is capable of arbitrarily rotating an imaging cross-section. The method is roughly classified into a contour extraction mode and a therapeutic mode. In the contour extraction mode, a contour extraction line of an object is drawn by using an ultrasonic static image, and two or more singularities are set. It is possible to estimate the motion of the object by focusing the motion of the singularities and reconstructing the contour from the positional relationship of the singularities. The focusing of the singularities and the reconstruction of the contour are conducted on plural different cross-sections of the object, and it is confirmed that a focal point of the therapeutic ultrasonic waves exists within the contour of the object. Then, the mode is shifted to the therapeutic ultrasonic waves, and the ultrasonic waves of the energy amount of which is obtained from a cauterization volume of a therapeutic region is irradiated. The movement (motion) of the therapeutic region is estimated from the breath or motion of the patient by a vibration meter or a ultrasonic monitor, and when the motion exceeds a predetermined threshold value, the irradiation of the ultrasonic waves is automatically stopped. Then, a process of setting the focal point is again repeated.
Also, in Patent Document 2 [Japanese Patent Laid-Open No. 2002-369888], a high-resolution three-dimensional image of an object is obtained before therapy, and the object is approximated by an ellipsoidal sphere. The two-dimensional cross-sectional image (elliptical shape) of the object is imaged in real time during therapy to obtain an in-plane barycentric motion and an area change of the object. The two-dimensional motion in the imaging region of the object is estimated from the barycentric motion. Also, the most matching position of the two-dimensional cross-sectional image that is obtained from the area change in the three-dimensional image that is approximated by the ellipsoidal sphere is determined to estimate the motion in a direction perpendicular to the two-dimensional cross-sectional image. According to the method, the three-dimensional motion is detected in real time, and the irradiation of the ultrasonic waves is controlled according to the presence or absence of the object in the therapeutic beam irradiated region.
As a diagnostic image device that displays an image which is necessary for diagnosis and therapy, there are an X-ray CT device (X-ray Computed Tomography), an MRI (Magnetic Resonance Imaging) device, a PET (Positive Emission Tomography) device, and an ultrasonic imaging device. Those imaging devices have relative merits different from each other according to the imaging region and imaging environments. The ultrasonic image is superior to the image obtained by other image acquisition means in the real time property, but suffers from a problem of the resolution as a therapy support image. On the other hand, the X-ray CT device, the MRI device, and the PET device are superior in the production of the functional information and resolution although the applied regions are different from each other, but suffers from a problem of the real time property as compared with the ultrasonic image.
The motion detecting technology obtains the positional information of the imaging cross-section of the ultrasonic transducer which changes according to the motion. An image obtained by other image acquisition means which corresponds to the imaging cross-section of the ultrasonic transducer is displayed by using the motion detecting technology, thereby making it possible to produce the optimum support image for the therapy which combines the ultrasonic cross-sectional image with an image obtained by other imaging means such as MRI or the X-ray image in real time.
Hereinafter, a description will be given of a conventional image producing device using the motion detecting method.
In Patent Document 3 (Japanese Patent Laid-Open No. 2003-144412), a high-resolution MRI three-dimensional image is obtained prediagnostically. Subsequently, a two-dimensional cross-sectional image of an object is imaged by using the ultrasonic diagnostic device. A characteristic region of the object such as the contour or blood vessels is extracted from the two-dimensional cross-sectional image thus obtained. The characteristic region thus extracted is run with the MRI three-dimensional image to ascertain the best matching position, and the two-dimensional cross-section is extracted. The extracted two-dimensional cross-section is deformed so as to coincide with the characteristic region and then displayed on an image display unit. In this manner, the ultrasonic image that is imaged in real time is replaced by an MRI image with a high resolution, thereby making it possible to display the high-resolution image in real time.
Also, Patent Document 4 (Japanese Patent Laid-Open No. 9-24034) discloses a system that conducts diagnosis and therapy within a shielded room of the MRI device. A marker that is measurable in the MRI and a clinometer for measuring an angle of the imaging region are fitted onto the ultrasonic transducer to ascertain the position of the imaging cross-section due to the ultrasonic transducer. The MRI image of the ascertained cross-section is obtained and displayed on an image display unit.    Patent Document 1: Japanese Patent Laid-Open No. 2000-237205    Patent Document 2: Japanese Patent Laid-Open No. 2002-369888    Patent Document 3: Japanese Patent Laid-Open No. 2003-144412    Patent Document 4: Japanese Patent Laid-Open No. 9-24034